1. Field of the Invention
The present invention relates to a device and a method of exchanging a tool between a tool holding device and a spindle which is capable of approaching and moving away from the tool holding device, the tool holding device having a plurality of tool holding members disposed at predetermined intervals. More particularly, the present invention relates to the device and method of exchanging a tool for use in a drilling machine for drilling a hole in a printed circuit board.
2. Description of the Prior Art
Hitherto, a conventional drilling machine for drilling a hole in a printed circuit board has been disclosed in Japanese Patent Unexamined Publication No. 62-94210. According to this disclosure, the conventional drilling machine has been arranged in such a manner that a tool holding device of a type disclosed in Japanese Utility Model Unexamined Publication No. 62-201638 and holding a plurality of drills is secured to a table of the drilling machine on which a printed circuit board is placed so that desired holes are drilled while exchanging the tool.
The conventional tool holding device of the type described above has an advantage that a multiplicity of tools can be held. However, the tool cannot directly be exchanged between the tool holding device and the spindle since the interval of the held tools is excessively reduced.
Therefore, the structure has been arranged in such a manner that a transfer station for transferring tools is provided for the tool holding device so that a tool held by the tool holding device is temporarily held by the transfer station and the tool is subsequently transfers from the transfer station to the spindle. Furthermore, the drill held by the spindle is temporarily returned to the transfer station before it is moved from the transfer station to the tool holding device.
However, the conventional tool holding device thus arranged has encountered a problem in that a long period of time is required to exchange the tools, lowering the working efficiency because the conventional tool holding device is arranged to send/receive tools via the transfer station.